This application is the U.S. national phase of International Application No. PCT/EP2019/078622 filed Oct. 22, 2019 which designated the U.S. and claims priority to DE Patent Application No. 10 2018 130 280.0 filed Nov. 29, 2018, the entire contents of each of which are hereby incorporated by reference.
The invention relates to a drying unit for drying printed substrates according to the preamble of claim 1.
A drying system for irradiation drying of paints and/or lacquers and/or coatings on substrates in printing and/or coating machines is known from DE 101 41 755 A1, consisting of a radiator module and an inerting chamber, wherein the inerting chamber consists of a base body, a nozzle system, lateral sealing elements and an inlet and an outlet element; the lateral sealing elements and the outlet element seal the inerting chamber against the sheet guiding cylinder, and the inlet element seals the inerting chamber against the cylinder gap between the sheet guiding cylinder and the cylinder upstream of the drying system when seen in the paper running direction, and a region permeable for the drying radiation is formed on the base body of the inerting chamber. For the drying processes, UV radiators or so-called Excimer UV radiators can be used as the radiator. Nitrogen is often used as the inert gas. With the target inerting, the remaining amount of oxygen is to be lowered to a value below one percent, if possible.
A drier working with Excimer radiators for drying and/or curing lacquers and/or paints on sheets in sheet printing machines is known from DE 198 57 984 A1, wherein the drier is allocated to the sheet conveyed on a sheet guiding cylinder along the sheet conveying path, and at least one Excimer radiator and at least one inert gas blower is surrounded by a bell, wherein the bell consists of lateral parts allocated to the sheet guiding cylinder on both sides and an upper region extending across the width of the sheet conveying path with an inlet and outlet part, and the bell encloses the interior chamber with the sheet guiding cylinder and with at least one further cylinder.
A printing unit without printing plates in a hybrid sheet offset printing machine for personalised printing of the printing sheets to be processed is known from EP 2 982 510 A1, wherein at least one inkjet printing head is integrated in a printing mechanism, in a lacquer mechanism, in an abutment region and/or in an outlay region of the hybrid sheet offset print machine, wherein, in the hybrid sheet offset print machine, printing sheets are printed in the offset printing process with a static single-coloured or multi-coloured printed image and according to the inkjet print method with a variable personalisation printed image, wherein a modular printing unit is provided which has at least one inkjet printing head and whose construction is variable, wherein the modular printing unit is formed from further module units in terms of its functional construction, and wherein the module units are selected and arranged in the hybrid sheet offset print machine so as to be able to be configured and positioned depending on a printing task posed and one or more selectable frame conditions at least by means of a parameter set from the predetermined printing subject, the quantity of editions to be printed, quality requirements of the printing, printing materials, coating materials, drying conditions.
A device for curing a printing ink, lacquer, adhesive or silicon layer is known from EP 0 830 217 B1, with which a substrate made of paper, plastic, glass, wood or metal is coated, having a housing which is open in the direction of a transport body transporting the substrate and which covers the substrate by maintaining substrate inlet and substrate outlet gaps, and having a UV lamp arranged inside the housing with a reflector, which directs the UV light towards the substrate passing through, wherein at least one flushing gas line is connected to a flushing gas source, on the one hand, and to the interior space of the housing, on the other hand, via a nozzle, wherein flushing gas nozzles that can be cooled with water are preferably provided close to the substrate inlet gap and the substrate outlet gap, the current direction angle of which can be set in relation to the substrate passing through and which is in current connection with a gas flow direction and quantity regulator, wherein a tempering device is provided to cool the substrate passing through, wherein the flushing gas nozzles are provided on the lateral walls of the housing, and wherein cooling channels or grooves are arranged in the housing, the reflector and the transport body.
An electron beam device arranged in a sheet printing machine for drying inks applied to printing sheets is known from JP H04-145400 A, wherein the drying chamber is filled with an inert gas (nitrogen).
An inerting device for radiator devices for drying and/or curing paints and/or lacquers within printing machines is known from DE 197 04 284 A1, wherein, in particular for sheet printing machines with Excimer radiators and blowing nozzles arranged inside the inerting chamber, wherein the blowing nozzles are formed to be able to be regionally restricted and/or switched off across the width of the printed material web, and a control device detecting the front and rear edge of the printing material and controlling blowing nozzles and/or Excimer radiators is superordinate to the blowing nozzles and/or Excimer radiators.
A method for printing is known from WO 2005/097927 A1 in which a printing ink is printed onto a substrate using an intaglio printing machine, in which the printing ink is cured after printing, in which the curing is carried out e.g. by an electron beam. This method is used e.g. to produce banknotes.
A method for producing a security element for a security paper, document of value or similar having a substrate is known from DE 10 2006 032 679 A1, wherein the substrate is at least partially equipped with a coating comprising at least two layers, having the following steps:
a) applying a first layer to the substrate,
b) applying at least one second layer to the first layer, wherein complete curing of the first layer is not carried out before applying the second layer,
c) embossing at least one layer of the coating,
d) curing the coating,
wherein applying the layers is carried out e.g. using a printing method, in particular gravure printing, flexographic printing or offset printing, wherein curing the layers is carried out e.g. by means of ultraviolet radiation and/or by means of electron radiation.
A device for treating a sheet-like substrate is known from DE 10 2016 200 544 A1, having a sheet guiding cylinder and an inerting device allocated to the sheet guiding cylinder, wherein the sheet guiding cylinder has first holding means for holding the front edge of the substrate, and second holding means are provided which hold the substrate on the sheet guiding cylinder in a region spaced apart from the front edge of the substrate, and wherein the substrate guided by the sheet guiding cylinder can be supplied with inert gas, wherein a third holding means is arranged outside the periphery of the sheet guiding cylinder.
The object of the invention is to create a drying unit for drying printed substrates, wherein the drying unit is suitable for as high a printing speed as possible in a printing machine in an industrial production process.
According to the invention, the object is solved by the features of claim 1. The dependent claims show advantageous embodiments and/or developments of the solution found.
The advantages that can be obtained using the invention consist, in particular, of the drying unit of the printing machine being suitable for as high a printing speed of the printing machine as possible in an industrial production process. Further advantages can be seen in the exemplary embodiments described.
Exemplary embodiments of the invention are depicted in the drawings and are described below in more detail.
Here are shown:
By way of example,
The sheet rotation printing machine printing in an intaglio printing method, in particular, depicted by way of example in
In order to achieve as high a printing speed as possible of e.g. 10,000 printing sheets 21 per hour using the printing machine described above by way of example in an industrial production process, the printing inks applied to the printing sheets 21 and/or the lacquer applied to the printing sheets 21 are preferably dried. Preferably, printing inks and/or lacquers that do not run, i.e. are viscous, are used. In the preferred embodiment, printing inks and/or lacquers that are radiation-cured are used. In a particularly preferred embodiment, printing inks and/or lacquers that do not include solvents and that can be cured by an electron beam are used. Such printing inks and/or lacquers polymerise with radiation by an electron beam within milliseconds and are thus dried in an extremely short period of time. A coloured film or lacquer film consisting of such printed inks and/or lacquers is polymerised completely and is thus also cured completely, such that, after drying, no fragments or residues of the split remain in the printing inks or lacquers, which could migrate somewhere else using the substrate 21. Printing inks or lacquers dried by an electron beam form an elastic, glossy coloured film or lacquer film which, in each case, is highly resistant to scratches and chemicals.
However, it is problematic in a drying method using an electron beam that the drying, i.e. the setting reaction, has to take place in an oxygen-reduced inert atmosphere, in which the amount of oxygen is at most 1% in order to obtain high production quality, preferably ranging from 300 ppm to 500 ppm, in particular ranging from 150 ppm to 250 ppm, where necessary even lower into the region of less than 50 ppm, wherein the amount of oxygen permissible in the inert atmosphere is dependent on the material of the substrate used and/or on the chemical composition of the printing ink(s) or lacquers used. In other circumstances, i.e. with a higher amount of oxygen, free radicals contained in the printing inks or lacquers that are still liquid, i.e. atoms or groups of atoms which each contain a free electron, would chemically react more quickly with the oxygen molecules contained in this air than among one another and would form only one incomplete, irregular cross-linkage. In normal ambient air, this is particularly true with an oxygen amount of about 21%. In an atmosphere with an oxygen amount of more than 1%, in particular in normal ambient air, the setting reaction leads to the printing inks or the lacquer still being damp, adhesive and without shine and having poor adhesion properties and only a low scratch resistance.
Good drying results are obtained in a drying unit 22 with an atmosphere reduced to an oxygen amount of at most 1%, in which an inert gas, i.e. a gas that is chemically very sluggish, i.e. an elementary gas such as nitrogen or a noble gas such as helium, neon, argon, krypton, xenon or radon or a gaseous molecular compound such as sulphur hexafluoride and carbon dioxide, suppresses the oxygen contained in the air. Oxidative processes are prevented by an inert gas as a result of the suppression or clear reduction of oxygen. Here and below—insofar as reference is made to the spatial content of the drying unit 22—the term “atmosphere” is referred to in its entirety as the gaseous medium that is oxygen-reduced by the inert gas, which is present in the drying unit 22 in a chamber provided for drying the printing inks or the lacquer.
The drying unit 22 has an electron beam generator 28 which is arranged in a vacuum chamber 29. The vacuum chamber 29 and the chamber 23 filled with the inert gas are spatially separated from one another by a window. The window has a seal 31, e.g. made of a titanium film with a material strength ranging from e.g. 0.01 mm to 0.3 mm, preferably at about 0.2 mm. The electron beam generator 28 has a cathode 32, e.g. in the form of a filament, and an anode 33 spaced apart from the cathode 32. Electrons emerging from the cathode 32 are accelerated by an electrical voltage placed between the cathode 32 and the anode 33 in the direction of the anode 33 virtually at the speed of light. The electrical voltage for accelerating the electrons lies in this region e.g. between 80 keV and 300 keV depending on a state, e.g. chemical composition, of the printing inks used and/or the desired penetration depth into these printing inks and/or on the material of the substrate 21 used. The energised electrons accelerated in this way penetrate the seal 31, consisting e.g. of a thin titanium film, of the window and hit preferably substantially perpendicularly on the printing sheets 21 guided past at this window in the chamber 23 containing inert gas. The energised electrons are quasi enclosed into the printed inks applied to the substrate 21. When these electrons impact on the printing inks applied to the substrate 21 with a layer thickness of e.g. about 0.1 mm and when the electrons penetrate into this colour layer, a chemical chain reaction is triggered in this printing method, in which short-chain acrylate molecules contained in the printing ink are connected to form long-chain polymers, whereby a cured coloured layer is formed in second fractional parts. The substrate 21 is not heated up. Because the energy of the electrons fired at the substrate 21 by the electron beam generator 28 is great enough to generate the first radicals in the printed inks and to initiate the polymerisation directly in the monomers (diluents) or oligomers (binding agents) of these printing inks, it is not necessary to add photo-initiators to the printing inks used, as would have been necessary e.g. for a UV drying process.
Oligomers used in printing inks suitable for gravure printing methods include, e.g. epoxy acylates, acrylated oils, urethane acrylates, polyester acrylates, silicone acrylates, acrylated amines, acryl-saturated resins and acryl acrylates.
Because of the high viscosity of most oligomers, diluents are required to reduce the overall viscosity of a printing ink cured by an electron beam and thus to support the handling and application of these printing inks, e.g. to make these printing inks suitable for wiping on the plate cylinder 06 by the wiping cylinder 07. Suitable diluents can include water or “reactive” monomers, which are incorporated in the relevant printing ink. Reactive monomers are typically acrylates and methacrylates and can be monofunctional or multifunctional. For example, multifunctional monomers would be polyester acrylates or polyester methacrylates, polyol acrylates or polyomethacrylates and polyether acrylates or polyether methacrylates.
Some examples for the respective composition of layers made of printing inks or lacquers which can be respectively dried by an electron beam follow:
Now, to carry out a radiation drying of printed inks or lacquers applied to the substrate 21, in each case with an electron beam in a printing machine for the industrial production of banknotes, security documents or security elements, some arrangement variants are now described below. In all these arrangement variants, the drying unit 22 has an electron beam generator 28 by means of which energised electrons are fired at the substrate 21.
A first arrangement variant provides to arrange the entire printing machine in an enclosure sealed with respect to the ambient air, wherein an inert atmosphere is provided with an oxygen amount of at most 1% inside the enclosure. The chamber 23, containing the inert gas, of the drying unit 22 is implemented here by the enclosure of the printing machine. The printing sheets 21 to be printed are supplied to the printing machine by an entrance floodgate formed on the enclosure and are discharged from the printing machine through an exit floodgate formed on the enclosure. In this first arrangement variant, the drying unit 22 is arranged at any position in the transport direction T of the substrates 21 formed, in particular, in each case as printing sheets 21, behind the printing gap 17 formed by the printing cylinder 04 and plate cylinder 06, e.g. also on or in the transport direction T of the printing sheets 21 after the transportation device 16, which is arranged after the printing mechanism 03 in the transport direction T of the printed sheets 21 and is formed e.g. as a peripheral transport strip or as a peripheral chain system or as a chain gripper system.
A second arrangement variant provides to arrange the drying unit 22 in the printing mechanism 03 of the printing machine. The chamber 23, containing the inert gas, of the drying unit 22 is here arranged in the printing mechanism 03 in such a way that at least one arc section of the printing cylinder 04 is arranged inside this chamber 23.
As depicted by way of example in
As illustrated by means of the second to fourth arrangement variants, the drying unit 22 having a chamber 23 containing the inert gas can be arranged, for example, in the printing mechanism 03 of the printing machine or on an intermediary cylinder 36; 37 arranged after the printing mechanism 03 in the transport direction T of the substrates 21 or on the transportation device 16 transporting the substrates 21 to a delivery 18.
By way of example,
As can be seen in
In a further design variant, it is provided that e.g. only one single pneumatic system is provided, wherein the same gaseous medium as in the chamber 23 of the drying unit 22 is provided for the required suction air for holding the substrates 21 to be transported on the outer surface of the suction cylinder 38, in particular during their entire dwelling time on the relevant suction cylinder 28. Thus, e.g. a rotation printing machine having at least one printing mechanism 03 for printing substrates 21 emerges, wherein the relevant printing mechanism 03 has at least two interacting cylinders 04; 06, wherein at least one of these cylinders 04; 06 is formed as a suction cylinder transporting the substrates 21 on its outer surface, wherein a pneumatic system for providing the required suction air for holding the substrates 21 to be transported on the outer surface of the relevant cylinder 04, 06 is provided. Here, in or after the relevant printing mechanism 03, a drying unit 22 is provided in the transport path of the substrates 21, wherein substrates 21 printed by the relevant printing mechanism 03 are guided or at least can be guided through a chamber 23 of this drying unit 22, wherein a gaseous medium that is oxygen-reduced by an inert gas is provided in the chamber 23 of the drying unit 22. Here, in an advantageous design, the suction air provided in the pneumatic system for holding the substrates 21 to be transported on the outer surface of the relevant suction cylinder is the same gaseous medium as in the chamber 23 of the drying unit 22. Preferably, one of the cylinders 04 interacting in the relevant printing mechanism 03 is formed as a printing cylinder 04 and the other cylinder 06 interacting with the printing cylinder 04 is formed as a plate cylinder 06 applying a printed image to the relevant substrates 21. In the very preferable design, the relevant printing mechanism 03 is formed as a printing mechanism 03 printing in a deep-draw printing process, in particular in a gravure printing process.
In the design variant according to
Since the provision of an inert gas, e.g. nitrogen, in a drying unit 22 involved in an industrial production process for electron beam curing is associated with considerable costs, the entrance provided for the substrates 21 into the chamber 23 of the drying unit 22 and/or the exit from this chamber 23 are each formed e.g. in the shape of slots and/or are each e.g. sealed by a doctor blade nozzle 24, in particular in the form of a nozzle beam or by a preferably flexible seal 34.
A further measure for minimising a leakage of the oxygen-reduced gaseous medium, in particular of inert gas, from the chamber 23 and/or an unwanted entering of oxygen from the ambient air into this chamber 23 is respectively covering, with a cover, channels 51 or grooves 51, which are formed on a cylinder at least partially, e.g. in a sheet section, passing through the chamber 23 of the drying unit 22, e.g. on a printing cylinder 04 or on a plate cylinder 06 or on an intermediary cylinder 36; 37 or on a suction cylinder 38. If at least one gripper for holding a substrate 21 on the respective outer surface of the relevant cylinder is arranged in such a channel 51 extending in particular transversely to the transport direction T of the substrate 21 across the width, the cover covering this channel 51 has a recess at the position of the relevant gripper. However, in terms of the leak-tightness of the chamber 23 of the drying unit 22, it is advantageous to form the relevant cylinder 04; 06; 36; 37; 38 respectively without a gripper, i.e. without a mechanical gripper, or, in the case of interacting cylinders 04; 06 such as the printing cylinder 04 and the plate cylinder 06, to form at least one of these cylinders 04; 06 without a gripper. Substrates 21 to be arranged on their respective outer surface are preferably held on cylinders 04; 06; 36; 37; 38 formed without grippers in each case only by suction air. Similarly, it is also advantageous to form a transportation device 16 formed as a transport strip without a gripper for transporting substrates 21.
Thus, e.g. a rotation printing machine having at least one printing mechanism 03 for printing substrates 21 emerges, wherein a drying unit 22 is provided in or after the at least one printing mechanism 03 in the transportation path of the substrates 21, wherein substrates 21 printed by the at least one printing mechanism 03 are guided or at least can be guided through a chamber 23 of this drying unit 22, wherein an atmosphere that is oxygen-reduced by an inert gas is provided in the chamber 23 of the drying unit 22, wherein the chamber 23 of the drying unit 22 surrounds at least one arc section of a cylinder 04; 06; 36; 37; 38 transporting the substrate 21 to be dried, wherein this cylinder 04; 06; 36; 37; 38 has at least one gripper for holding one of the substrates 21 on the outer surface of the relevant cylinder 04; 06; 36; 37; 38 in a channel 51 extending transversely to the transport direction T of the substrates 21, wherein the relevant channel 51 is covered by a cover, where in the cover has a recess at the position of the relevant gripper, wherein the relevant cylinder 04; 06; 36; 37; 38 has at least one further holding element for holding the relevant substrate 21 on the outer surface of the relevant cylinder 04; 06; 36; 37; 38 on its outer surface in addition to the at least one gripper.
Alternatively, e.g. a rotation printing machine having at least one printing mechanism 03 for printing substrates 21 emerges, wherein a drying unit 22 is provided in or after the at least one printing mechanism 03 in the transport path of the substrates 21, wherein substrates 21 printed by the at least one printing mechanism 03 are guided or at least can be guided through a chamber 23 of this drying unit 22, wherein an atmosphere that is oxygen-reduced by an inert gas is provided in the chamber 23 of the drying unit 22, wherein the chamber 23 of the drying unit 22 surrounds at least one arc section of a cylinder 04; 06; 36; 37; 38 transporting the substrates 21 to be dried, wherein this cylinder 04; 06; 36; 37; 38 is formed without a gripper.
A particular embodiment variant is e.g. a rotation printing machine having at least one printing mechanism 03 for printing substrates 21, wherein a drying unit 22 is provided in or after the at least one printing mechanism 03 in the transport path of the substrates 21, wherein substrates 21 printed by the at least one printing mechanism 03 are guided or at least can be guided through a chamber 23 of this drying unit 22, wherein an atmosphere that is oxygen-reduced by an inert gas is provided in the chamber 23 of the drying unit 22, wherein several suction rollers 48 are arranged in the chamber 23 of the drying unit 22 along the transport path of the substrates 21, wherein the suction rollers 48 convey the substrates 21 through this chamber 23 by their respective rotation.
A concrete embodiment variant is also given e.g. by a sheet printing machine having at least one printing mechanism 03 for printing printed sheets 21, wherein a drying unit 22 is provided in or after the at least one printing mechanism 03 in the transport path of the printed sheets 21, wherein printed sheets 21 printed by the at least one printing mechanism 03 are guided or at least can be guided through a chamber 23 of this drying unit 22, wherein an atmosphere that is oxygen-reduced by an inert gas is provided in the chamber 23 of the drying unit 22, wherein the drying unit 22 has an electron beam generator 28 for drying the printed printing sheets 21 by means of an electron beam directed into the chamber 23, wherein the atmosphere in the chamber 23 of the drying unit 22 has an oxygen amount of at most 1%.
Furthermore, e.g. a sheet gravure printing machine having at least one printing mechanism 03 for printing sheets 21 emerges, wherein a printing cylinder 04 and a plate cylinder 06 interacting with this printing cylinder 04 are arranged in the relevant printing mechanism 03, wherein a wiping cylinder 07 activated or at least being able to be set against the plate cylinder 06 is provided, wherein a drying unit 22 is provided in or after the at least one printing mechanism 03 in the transport path of the printed sheets 21, wherein printing sheets 21 printed by the at least one printing mechanism 03 are guided or at least can be guided through a chamber 23 of this drying unit 22, wherein the drying unit 22 has an electron beam generator 28 for drying the printed printing sheets 21 by means of an electron beam directed into the chamber 23.
Further embodiments and/or developments of the printing machines mentioned above emerge by means of any meaningful and thus consistent combination of the features described above by way of example.
In an advantageous development, the two cylinders 04; 06 set against each other form a printing mechanism 03 at the entrance of the chamber 23, wherein one of the cylinders 04 is formed as a printing cylinder 04 and the other cylinder 06 as a plate cylinder 06 interacting with the printing cylinder 04 and applying a printed image to the relevant substrates 21. Here, the printing mechanism 03 formed at the entrance of the chamber 23 of the drying unit 22 is formed e.g. as a printing mechanism 03 printing in a gravure printing method, in particular in an intaglio printing method.
Advantageously, a transportation device 16 is provided, wherein the transportation device 16 is arranged to guide the substrates 21 through the chamber 23, wherein the transportation device 16 is formed as a preferably peripheral transportation strip or a preferably peripheral chain system, in particular as a chain gripper system. It can also be provided that at least one of the two cylinders 04; 06 set against each other at the entrance of the chamber 23 is formed as a suction cylinder. Alternatively or additionally, in a channel 51 extending transversely to the transport direction T of the substrates 21, e.g. at least one of the two cylinders 04; 06 set against each other at the entrance of the chamber 23 has at least one gripper for holding one of the substrates 21 on the outer surface of the relevant cylinder 04; 06. Here, the relevant channel 51 is preferably covered with a cover, wherein the cover has a recess at the position of the relevant gripper.
Number | Date | Country | Kind |
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10 2018 130 280.0 | Nov 2018 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2019/078622 | 10/22/2019 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2020/108864 | 6/4/2020 | WO | A |
Number | Name | Date | Kind |
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3431139 | Joachim | Mar 1969 | A |
9738472 | Rothaug | Aug 2017 | B2 |
9889644 | Hachmann | Feb 2018 | B2 |
20110205321 | Kobayashi | Aug 2011 | A1 |
20140299448 | Maul | Oct 2014 | A1 |
20150246525 | Maul | Sep 2015 | A1 |
20160271933 | Feygelman | Sep 2016 | A1 |
Number | Date | Country |
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197 04 284 | Oct 1998 | DE |
198 57 984 | Jun 2000 | DE |
100 83 500 | Jan 2002 | DE |
101 41 755 | Mar 2002 | DE |
10 2006 032 679 | Jan 2008 | DE |
10 2015 116 491 | Mar 2016 | DE |
10 2016 200 544 | Dec 2016 | DE |
0 830 217 | Nov 1999 | EP |
1 995 062 | Nov 2008 | EP |
2 982 510 | Feb 2016 | EP |
2 987 634 | Feb 2016 | EP |
4-145400 | May 1992 | JP |
03020522 | Mar 2003 | WO |
2005097927 | Oct 2005 | WO |
Entry |
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International Preliminary Report on Patentability for PCT/EP2019/078622 dated Oct. 13, 2020, 11 pages. |
International Search Report for PCT/EP2019/078622 dated Dec. 17, 2019, 7 pages. |
Written Opinion of the ISA for PCT/EP2019/078622 dated Dec. 17, 2019, 8 pages. |
Number | Date | Country | |
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20210323300 A1 | Oct 2021 | US |